A metal layer having a thickness of several tens of nanometers to several hundreds of nanometers, such as aluminum or chromium, is sometimes provided on the surface of thermoplastic resin molded products such as automotive parts and electric device housings by the vacuum deposition method, the sputtering method or the like in order to enhance the designability and functionability.
In recent years, a method of directly vapor-depositing a metal on the surface of a thermoplastic resin molded product without providing an undercoat layer, the so-called “direct vapor deposition method”, has been employed in order to simplify processes. Since the designability of a molded product on which a vapor deposition layer is deposited by the direct vapor deposition method varies depending on the kind of a resin material of and the surface condition of the molded product on which a vapor deposition layer is deposited, it is important that the molded product surface before the vapor deposition layer is deposited has no haze and a beautiful bright appearance. Particularly in molded products in which a rubber is blended, a decrease in glossiness, and haze often occur.
In the case where a large-sized molded product is injection-molded, when a resin is injected into a die from a nozzle, there is a difference in molding rates of the resin in the die between the vicinity of the nozzle and the vicinity of the terminal depending on the conditions. In order to uniformize the appearance such as glossiness of a large-sized molded product, it is essential that there is no difference in the surface state of an obtained molded product across the entire surface of the molded product, specifically, across the vicinity of the nozzle to the vicinity of the terminal of the die. Hence, for molding a large-sized molded product, a thermoplastic resin composition is demanded which has a low dependency on the molding rate, that is, a small variation in the surface state even if the molding rate is varied.
Tail lamps, stop lamps, head lamps and the like for automobiles are so configured that a lens member composed of a transparent resin such as a polymethyl methacrylate (PMMA) or a polycarbonate (PC), which refracts light from a bulb as a light emission body, and a housing member supporting the lens member accommodate the bulb. For joining the lens member and the housing member, the hot plate welding method is often used because the method does not use an adhesive, and has only a small number of processes and is simple. The hot plate welding method involves pressing a fluororesin-processed, metal-made or another hot plate on each portion to be joined of thermoplastic resin molded products for several seconds to make a melted state, and thereafter quickly separating the hot plate and joining the both. In the hot plate welding method, when the hot plate pressed on a molded product is separated, parts of a melted resin fuses on the hot plate and the so-called stringing occurs in some cases. In adopting the hot plate welding method, in order to make the appearance of a joining portion beautiful, little stringing is very important.
As resin compositions for molded products causing little of such stringing and suitable for the hot plate welding method, reported are a resin composition containing a graft copolymer obtained using a composite rubber composed of a polyorganosiloxane and a poly(meth)acrylate, a resin composition containing a graft copolymer obtained using a dienic rubber, and other resin compositions (Patent Documents 1 to 5).
However, vapor deposition layers formed by the direct vapor deposition method are demanded to exhibit a further brightness. Joining portions by the hot plate welding method are requested to exhibit a more beautiful appearance. Further, housing members of automotive lamps are requested to have weatherability of a high level; and use of a resin composition containing a graft copolymer obtained using a dienic rubber does not provide a sufficient weatherability in some cases.    Patent Document 1: Japanese Patent Laid-Open No. 2006-028393    Patent Document 2: Japanese Patent Laid-Open No. 2005-314461    Patent Document 3: Japanese Patent Laid-Open No. 2003-128868    Patent Document 4: Japanese Patent Laid-Open No. 2006-111764    Patent Document 5: Japanese Patent Laid-Open No. 09-194681